Refrigeration

Refrigeration (from the Latinfrigus, frost) is generally the cooling of a body by the transfer of a portion of its heat away from it. Applications include conservation, especially of food, and lowering the temperature of drinks to one that is more agreeable for consumption. Refrigerators are common in kitchens, with separate sections or separate machines for cooling and freezing.

Cooling of something hot is often done by means of material at ambient temperature, for example the fan cooling of computer equipment.

Where temperatures below that of any available natural cooling agent are required, refrigerators are used to produce the required cooling effect by taking in heat at low temperatures and rejecting it at temperatures somewhat above that of the natural cooling agent, which is generally water or air. The function of a refrigerating machine, therefore, is to take in heat at a low temperature and reject it at a higher one, using external energy to drive the process. A refrigerator is effectively a heat pump, a heat engine running in reverse. It is also possible to use eutectic salts.

The gas absorption refrigerator, which cools by the use of a source of heat, was invented in Sweden by Baltzar von Platen in 1922. [1] It was later manufactured by Electrolux and Servel. Today it is used in homes that are not connected to the electrical grid, and in recreational vehicles.

In the newest models, an LCD display suggests what types of food should be stored at what temperatures and shows the expiry date of the food stored.

Some models include a system to warn of a power failure, with a memory function that alerts the user to the failure by flashing the temperature display. Once the user presses an information key, the maximum temperature reached during the power failure is displayed, along with information on whether the frozen food has defrosted or whether it can be stored without having developed dangerous bacteria.